import os
import subprocess
import sys

def extract_audio(video_path, output_path=None):
    """
    Extracts audio from a video file using ffmpeg.
    
    Args:
        video_path (str): Path to the input video file.
        output_path (str, optional): Path for the output audio file. 
                                     If None, defaults to same name with .wav extension.
    
    Returns:
        str: Path to the generated audio file.
    """
    if not os.path.exists(video_path):
        raise FileNotFoundError(f"Video file not found: {video_path}")

    if output_path is None:
        base_name = os.path.splitext(video_path)[0]
        output_path = f"{base_name}.wav"

    # Check if output file already exists to avoid redundant processing
    if os.path.exists(output_path):
        print(f"Audio file already exists: {output_path}")
        return output_path

    print(f"Extracting audio from {video_path}...")
    
    # Command matching the user's preferred settings: 16kHz, Mono, PCM s16le
    # -y overwrites without asking (though we checked existence above, this is for safety if we force it)
    command = [
        "ffmpeg",
        "-i", video_path,
        "-ar", "16000",
        "-ac", "1",
        "-c:a", "pcm_s16le",
        "-y",
        "-v", "error", # Less verbose
        output_path
    ]

    try:
        subprocess.run(command, check=True)
        print(f"Audio extracted to: {output_path}")
        return output_path
    except subprocess.CalledProcessError as e:
        print(f"Error extracting audio: {e}")
        sys.exit(1)

def embed_subtitles(video_path, srt_path, output_path=None):
    """
    Embeds subtitles into the video file (Soft Subs) and sets them as primary.
    
    Args:
        video_path (str): Path to the input video.
        srt_path (str): Path to the SRT file.
        output_path (str, optional): Path for the output video.
    """
    if not os.path.exists(video_path) or not os.path.exists(srt_path):
        print("Error: Video or SRT file not found for embedding.")
        return

    if output_path is None:
        base, ext = os.path.splitext(video_path)
        output_path = f"{base}.subbed{ext}"

    print(f"Embedding subtitles into: {output_path}...")
    
    # Determine subtitle codec based on container
    sub_codec = "mov_text" if video_path.lower().endswith(".mp4") else "srt"

    # Command breakdown:
    # -map 0:v -map 0:a  -> Keep all video and audio from source
    # -map 1:0           -> Add the subtitle from the 2nd input (srt_path)
    # -c copy            -> Copy video/audio streams (no re-encoding)
    # -disposition:s:0 default -> Make the first subtitle track (ours) the default
    # -metadata:s:s:0    -> Set metadata for the first subtitle stream
    
    command = [
        "ffmpeg",
        "-i", video_path,
        "-i", srt_path,
        "-map", "0:v",
        "-map", "0:a",
        "-map", "1:0",
        "-c", "copy",
        "-c:s", sub_codec,
        "-disposition:s:0", "default",
        "-metadata:s:s:0", "language=eng",
        "-metadata:s:s:0", "title=English (AI Translated)",
        "-y",
        "-v", "error",
        output_path
    ]

    try:
        subprocess.run(command, check=True)
        print(f"Subtitles embedded successfully: {output_path} (Set as primary)")
    except subprocess.CalledProcessError as e:
        print(f"Error embedding subtitles: {e}")